This invention relates generally to improvements in spindle motors for use in computer disk drives and the like for rotatably driving one or more memory storage disks. More particularly, this invention relates to an improved disk drive spindle motor designed for integration directly into the spindle hub of a computer disk drive while providing sufficient driving torque to rotatably drive a stack of several memory storage disks.
In recent years, microcomputer equipment particularly such as so-called personal and desk top computers have become extremely popular for a wide variety of business and educational and other uses. Such computers commonly include a main central processor unit having one or more memory storage disks for storage of data. In many modern computers the storage disk or disks, sometimes referred to as "hard disks," are provided as part of a Winchester-type disk drive unit having the storage disks supported in a stack on a rotary spindle within a substantially sealed disk drive housing. The disks are rotatably driven in unison by a small spindle motor, and one or more electromagnetic heads on a movable positioning arm are displaced by a precision stepper motor to traverse surfaces of the rotating disks for purposes of reading and writing data. Such Winchester-type disk drive units are generally preferred in comparison with so-called floppy type disk drives due to their higher memory storage capacities and faster operating speeds.
With the steadily increasing popularity of personal sized computers, various standard computer components have evolved to accommodate installation into computers produced by different manufacturers and/or to insure compatibility with commercially available software In this regard, Winchester-type disk drive units having one or more memory storage disks of an approximate 5.25 inch diameter have been manufactured and used on an industry-wide basis. More recently, smaller and lighter Winchester-type disk drives having storage disks of about 3.74 inches in diameter have become available. For either diametric size, the disk drive units have been produced in standardized vertical profile sizes to permit installation into a computer as an original equipment item, or as an after-market item to replace or upgrade an original disk drive unit. Specifically, disk drive units have been manufactured with a vertical dimension of about 3.25 inches to fit within a so-called "full height" vertical spacing, or with a vertical dimension of about 1.625 inches to fit within a so-called "half height" profile.
For any specific disk drive unit, the total memory storage capacity is related in large degree to the number of disks mounted within the disk drive housing. However, particularly for low profile "half height" disk drives, the number of storage disks which will fit within the available space together with the required spindle motor is extremely limited In this regard, disk drive spindle motors have traditionally been mounted in an underslung geometry positioned within the disk drive housing immediately below the storage disk or disks. Such underslung spindle motors have provided adequate drive torque to insure rapid disk rotational start-up and to achieve the desired high speed disk operation typically at about 3,000-3,600 rpm. However, these underslung spindle motors occupy a significant portion of the vertical profile of the disk drive, and thereby further restrict the number of disks which can be used. Alternate spindle motors have been proposed wherein a compact motor is incorporated directly into the spindle hub of the disk drive, thereby freeing vertical space to be occupied with additional storage disks. However, such in-hub spindle motors have generally suffered from inadequate drive torque which has precluded their use with an optimized stack of storage disks.
There exists, therefore, a significant need for improvements in spindle motors of the type used in computer disk drives, wherein the spindle motor is designed for in-hub mounting while providing sufficient drive torque for rotatably driving a maximum plurality of storage disks. The present invention fulfills these needs and provides further related advantages.